Atmospheric storage mechanical weight batch blending plant

ABSTRACT

An atmospheric storage mechanical weigh batch blend plant is shown with atmospheric storage for providing a dry, pre-blend, oilfield cement ready for mixing at the wellhead for slurry injection into a well head upon adding the proper amount of water and other fluids. The batch blend plant has three separate weighing mechanisms for (a) larger or bulk quantity materials, (b) intermediate quantities of materials, and (c) small amounts of additives to be included to the mixture. The entire weigh batch blend plant can be disassembled and moved. A special pressurized air bearing is used in the blender.

FIELD OF THE INVENTION

The present invention relates to a dry cement batching and blendingplant, and more particularly, to a portable dry cement batching andblending plant that will accurately measure and completely blend theingredients of dry pre-made cement mixtures, which are then mixed withwater at the well site for the oil & gas drilling and fracturingindustry.

BACKGROUND OF THE INVENTION

A practice of using cement in the oil industry began around 1903 inCalifornia in an attempt to stop water from flowing into the oil well,and oil and gas from entering the waterways (aquifers). In those earlyyears, cement was hand mixed and run into a dump baler to the spotneeding to be plugged. Pumping cement, which would be mixed with water,down a well was soon also recognized as beneficial to encase the welland achieve a safer and more efficient operation of the drillingprocess. A forerunner of the modern two (2)-plug method was first usedin 1910. The two (2) plugs minimize mud contact with the cement.Although both mechanical and chemical improvements have been made in acementing process, the original plug concept is still valid today.

Erle Halliburton cemented a well in Oklahoma's Hewitt Field in 1920. Thedry blending of oilfield cements is attained by many means, but the mostprevalent remains the pneumatic transfer of the individual constituentparts of cements and additives, which are moved from pressure vessel topressure vessel. This remains very similar to what was developed in the1920's. These moves are often layered or “pancaked” to affect somewhatof a blend when then transferring to the next in a series of tanks. Thistype of mixing is referred to as “moves”. Moves result in a veryunscientific and haphazard blending methodology, as the differingspecific gravities and molecular makeup of the varies constituentmaterials including various cements, bulk powder additives andgranulated minerals and chemicals, are not easily comingled. Cementblends produced in this manner are highly dependent on the experienceand attention of the blend plant operator. Numerous problems have beenencountered with variations in such un-uniform blending which results inthe ununiformed blends needing to be “spiked” or modification of thecement blends at the well site prior to mixing with water to get aproperly performing and more complete mixture. A poor cement blendmixture can cause many problems including poor set strength, inadequatecement bond, blowouts, poor formation fracing or lack of muddisplacement, which in the least presents environmental hazards, andlosses in productivity, and in the worst cases can result in severeinjury and loss of life due to blowouts and resulting explosions andfire.

Because of the inconsistencies in the mix cement product, many oilfieldoperators have gone to “pod” or “batch mixing”. In the pod or batchmixing, all of the ingredients for the cement are put inside of a mixerand stirred together. This mix of blended cement is taken either in aslurry form or a powder form to the wellhead. At the wellhead, if it'sin the powder form, water is added as the slurry is injected into thewell. The using of pod or batch plants solved to some degree thecementing problems at shallow depths.

However, over the years, many different types of cements have beendeveloped. The American Petroleum Institute recognizes Class A throughClass J of different types of cements. When deciding upon cement job notonly does a type of cement have to be selected, but so does the variousadditives. Many different additives have developed over the years. Oilwells have gotten deeper and deeper, and in recent years drilling isboth vertical and horizontal, so the cementing occurs at higherpressures and higher temperatures, and the correct cement blend ormixture becomes more and more critical. Each well service companyprovides its own particular blend or “recipe” for their cement jobs,especially cement used at depths of 10,000 feet or more and are expectedby well owners to provide a high level of quality assurance ofhigh-performing well encasement with the pre-blended cements. Theinvention allows the utmost in quality assurance to the well servicecontractor, the well owner, landowner, and the community as a whole,while protecting the well rig workers and the environment.

For the blends used at high pressures and temperatures, it becomesimportant to completely mix (1) large volumes by weight items in thepre-blended dry cements, (2) intermediate volumes by weight of someitems in the pre-blended dry cements, and (3) small volumes by weight ofadditives in the pre-blended cements. All of these must be perfectlypre-blended together to give the ideal cement blend at the well siteprior to mixing with water or other fluids. If the ideal dry cementpre-blend is not reached and the cements and additives are not properlyapplied, blowouts can occur such as the BP Petroleum blowout thatoccurred in the Gulf of Mexico in 2010. Since the catastrophic BPblowout, more and more attention has been given to the accuracy of thepre-blend of cement being used, especially in deep wells, and infracturing of wells, and also on offshore drilling.

In an attempt to solve the problem of inadequate pre-blending ofoilfield cement, many of the larger companies have developed their ownsystem or techniques. For example, Schlumberger Technology Corporationin U.S. Pat. No. 7,464,757, shows a batch mixing facility to deliverhomogenized mixing slurry to a well pumping system, but this mixing canonly affect the water/fluid-cement ratios and homogenize the mixturewith the fluid, and does nothing to affect the imbalance of poorlypre-blended dry cements delivered to the well mixer out of specificationof the recipes and safety requirements.

One of the problems with the prior systems is when water is added to thecement mixture, the resulting slurry can only be as good as the drypre-blend, which at present is most unscientific and haphazard resultingin varying quality and unknown performance of the well encasement.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus to givea measured, dry, and completely pre-blended oilfield cement andadditives recipe that can be substantiated in a controlled andmeasurable fashion as to provide expected performance when mixed withfluids at the well site.

It is another object of the present invention to provide a method forweigh-batching and exacting measurement of all constituent materialsmaking up the oilfield cement according to a predetermined formula—by acomputerized and controlled method.

It is yet another object of the present invention to provide a portablepre-blend dry oilfield cement plant that can accurately blend a drycement to a measurable quantity by weight according to a predeterminedformula.

It is yet another object of the present invention to provide a portableblending plant that can blend a dry cement mixture that has (1) bulkingredients, (2) intermediate ingredients and, (3) small amountingredients, each being measured by weight, into a complete pre-blend asto allow for multiple small parts to be thoroughly interspersedthroughout the mass of the pre-blend.

It is yet another object of the present invention to provide a blenderthat can blend large quantities of dry cement mixtures to provide acompletely blended homogeneous dry pre-blended bulk ready-to-mixspecialized cement for mixing with fluids at the wellhead.

In the blending plant a collection of bulk storage tanks are arrangedaround a weigh batcher. Mechanical screw augers connect from each of thebulk storage tanks to the weight batcher to provide an automated andrecordable dosing of each constituent bulk powder to be blended. Theweigh batcher measures by weight a predetermined quantity from selectedbulk storage tanks. The measured quantities are then fed to a mechanicalblender of a batch-type providing for a consistent and recordablequantity and batch number allowing for traceability and subsequentquality assurance practices so badly required in oilfield wellencasement practices to date.

Intermediate quantities of ingredients for the cement blend are alsoweighed and fed into the blender. The intermediate quantities arenormally delivered in bulk sacks or bags, rather than in truckloads asfor the bulk storage tanks.

Also, small amounts of ingredients to be added to a cement mixture arealso weighed and delivered to the blender through a drag tubeconveyor—nothing is left to hand-add measurements or human error in theinvention. The blending plant then automatically and thoroughlymechanically blends under only atmospheric conditions all of the dryingredient-types (large, intermediate and small in quantities) into adry homogeneous pre-blend. As soon as the blending is complete, theblender dumps the batch into appropriate weighed and automaticallyinventoried containers; and starts the blending process begins again ina cycle basis to automatically pre-blend a prescribed total pre-blendquantity of several tons for shipment by bulk transport truck orspecialized oilfield bottle truck chassis to the well site.

Because the dry cement blend is very abrasive it can damage the bearingson any blender shaft used in a horizontal shaft equipped blender. Also,because any lubricant, such as grease, coming into contact with thecement blend can damage the cement blend, a special bearing was designedthat uses pressurized air to (a) keep the cement mixture out of thebearing and (b) provide an air cushion on which the bearing will turn.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrated perspective view of an atmospheric mechanicalweigh batch blend plant.

FIG. 2 is a top view of FIG. 1.

FIG. 3 is a perspective view of the blender used in FIGS. 1 and 2.

FIG. 4 is an illustrated perspective view of the mini batch portion ofthe weight batch blend plant shown in FIGS. 1 and 2.

FIG. 5 is a perspective view of the weigh vessel for measuringintermediate quantities of cementing ingredients of the weight batchblend plant shown in FIGS. 1 and 2.

FIGS. 6A and 6B are illustrated flow diagram of the weigh batch blendplant shown in FIGS. 1 and 2.

FIG. 7 is a cross-sectional view of a bearing used in the blender shownin FIG. 3.

FIG. 8 is an illustrated flow diagram of the atmospheric storagemechanical weigh batch blend plant.

FIGS. 8 a through 8 i illustrate electrical controls for the atmosphericstorage mechanical weigh batch blend plant of FIG. 8.

FIG. 9 is a top view of an alternative vertical blender.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2 in combination, an atmospheric storagemechanical weigh batch blend plant, representing by reference numeral12, is shown. All of the ingredients of the cement recipe aremechanically forced together inside of the blender 14.

1. Bulk Materials

The larger constituent quantities of materials that are needed in a drypre-blended cement, which are referred to as bulk materials, are storedin atmospheric bulk storage tanks 20A-20F. Bulk materials are receivedfrom bulk weigh batcher 16 via dual screw transport augers 18.Mechanical screw augers 22A-22F feed preselected bulk materials fromeither bulk storage tanks 20A-20F, respectively, into the bulk weighbatcher 16. Only preselected amounts of each bulk material from bulkstorage tanks 20A-20F is fed into the bulk weigh batcher 16 as isdetermined by weight. Thereafter, the weighed amount of each bulkmaterial from bulk storage tanks 20A-20F is fed via dual screw auger 18into the blender 14.

Each of the bulk storage tanks 20A, 20C, 20D and 20F contain a singlebulk material and have dust collectors 24 on the top thereof. When thebulk storage tanks 20A, 20C, 20D and 20F are being filled via vortexelbows 26 and air inside of the bulk storage tank 20 is being displaced,dust collectors 24 prevent dust from being discharged to the atmosphere.

Referring to bulk storage tanks 20B and 20E, these tanks are split downthe middle by dividing wall (not shown) so they can store two differentbulk materials. Therefore, two dust collectors 28 and 30 are required aswell as two vortex elbows 32 and 34 for split bulk storage tanks 20B and20E.

The use of the weigh batcher 16 with the mechanical screw augers 22where a large amount of the bulk material contained in bulk storage tank20 may be used, the large amount of material can be accurately weighedand fed through dual screw augers 18 into the blender 14.

2. Intermediate Materials

In a typical blend of dry cement that is to be used in deep wells withhigh pressure and temperatures, there will probably be some intermediatematerials by weight in the mix. By intermediate there will not be asmuch as the bulk materials, but will be more than small amounts. Theintermediate materials normally come in bulk bags rather than by thetruckloads. The intermediate materials are storage in intermediatestorage tank 36 that has a divided wall 38 to divide the intermediatestorage tank 36 into two separate halves for two different intermediatematerials to be included in the dry mixed cement. Each side of theintermediate storage tank 36 has a bulk bag unloader 40A and 40B. Thebulk bag unloaders 40A and 40B connect to drag tubes 42A and 42B,respectively, that delivers the intermediate material to the respectivesides of the intermediate storage tank 36 via discharge valves 44A and44B, respectively.

When the intermediate storage tank 36 is being filled up, dustcollectors 46A and 46B insure that no dust is discharged to theatmosphere as air inside of the intermediate storage tank 36 isdisplaced.

If the particular recipe calls for some of the intermediate materialscontained in intermediate storage tank 36, the intermediate materialsare discharged to a weigh vessel 48 contained there below (see FIG. 1).The weigh vessel 48 measures by weight an accurate amount of theintermediate material called for from the intermediate storage tank 36.Once properly weighed, the intermediate materials are moved bymechanical screw auger 50 to the blender 14.

3. Adding Small Amounts to Mixture

As wells are getting deeper, temperatures increasing and pressuresincreasing, a number of additives are combined in the recipe in smallamounts. The additives could perform many of the following functions:

-   -   1. Being an accelerator to shorten the setting time;    -   2. Be a retardant that lengthens the setting time;    -   3. Increase the density (weight) of the cement blend;    -   4. Decrease the density of the cement;    -   5. Change the compressive strength of the cement;    -   6. Change the flow properties of the cement;    -   7. Change the dehydration rate of the cement;    -   8. Extend the cement to decrease the cost of cementing;    -   9. Be an anti-foam additive to prevent foaming;    -   10. Include bridging material to plug lost circulation zones.

The above listing is just a typical listing of the functions of variousadditives that maybe included in the cement blend recipe. For thematerials that are added in small amounts, also called “additives”, theadditives are added in the mini batch facility 52, which is shown inmore detail in FIG. 4. The mini batch facility 52, has a series of weighvessels 54A-54C in which small amounts of an additive can be accuratelyweighed and then fed into the drag tubes 28.

Sometimes it is necessary to add an additive by hand, either because itis such a small amount or a decision was made at the last minute toinclude another additive. In that case, a hand add-on station 58 isprovided where the addition can be weighed as added by personneloperating the plant, by hand, on scale 60 and added through the hatch62. The small additives are delivered via the drag tubes 56 to theblender 14. The drag tube 56 moves the small amounts (additives) througha discharge housing 64 where the additives drop through additive tube 66into the blender 14 (see FIG. 3).

By use of these three separate weighing systems, (1) for the bulkmaterials, (2) intermediate materials, and (3) the small additives, avery accurately measured dry cement material is delivered to the blender14.

Referring now to FIG. 3, a large view of blender 14 is shown. The bulkmaterials are fed into the blender 14 through the dual screw augers 18.The intermediate materials are fed into the blender 14 through themechanical screw augers 50. The small amounts additives are fed into theblender 14 via the drag tubes 56, discharge housing 64 and additivestube 66. A vent 68 that has dust collection therein, allows any airinside of the blender 14 to be displaced as the materials are added.

The blender 14 is a dual shaft blender with two shafts 70 extendinghorizontally through the blender. Specially designed bearings 72 are oneach end, as will be discussed subsequently, of the shafts 70. Theshafts 70 are turned by blender motor 74 (see FIG. 2). Extending fromthe top the blender 14 is ducting 76 that provides displaced atmospherecontaining dust to be scavenged in a dust collection device called theblender scavenger—a pollution control device.

Referring now to the mini batch facility 52 is shown in FIG. 4, enlargedview of the weigh vessel 54 is shown in FIG. 5. The weigh vessel 54 ison a stand 78 with the drag tubes 56 (see FIGS. 1, 2, and 4) extendingthere below. The exact amount of a small additive that is desired is fedinto the weigh vessel 54 through opening 80 and then discharged into thedrag tubes 56. The weigh vessel 54 ensures that exactly the right amountof an additive is fed into blender 14 for the correct mixture or“recipe” for the dry pre-blended oilfield cement.

Referring to FIGS. 6A and 6B, a pictorial flow diagram of the variousfunctions on the weigh batch blend plant 12 are shown. The samereference numbers as previously used will be used again, plus newreference numbers for new items. To the far left of FIG. 6A is theintermediate storage tank 36 with dust collectors 46A and 46B beinglocated there above. The dividing wall 38 separates intermediate storagetank 36 into two halves. Bulk bags un-loaders 40A and 40B are used toload the intermediate storage tank 36 with the intermediate materialsthat are normally delivered in bulk bags. Mechanical screw 50 is used todeliver the intermediate materials to the hopper 82 of the blender 14.

Depending upon the number of intermediate materials that need to beintroduced into the blend, a number of intermediate storage tanks can beincreased as the desired. A typical number would be two (2) intermediatestorage tanks 36 each having two halves, which would then accommodate atotal of four different intermediate materials for the concreteblend—although this number may be reduced or added to accordingly as toaccommodate blend recipes as required.

Weigh vessel 54 is used to put small amounts of additives into theconcrete blend. Any number of weigh vessels 54 as is shown in mini batchfacility 52 (see FIG. 4) can be added as needed. The additives are fedthrough drag line 56 into the blender 14. In a typical example there maybe approximately four (4) weigh vessels 54.

The larger amounts of material that are delivered by truckloads will bestored in bulk storage tanks 20. Dust collectors 24 keep the dischargeof dust from the bulk storage tanks 20 from getting into the atmosphereduring loading and unloading. Materials delivered from bulk storagetanks 20 are weighed in a bulk weigh batcher 16 (see FIG. 2), thendelivered via dual screw auger 18 to the hopper 82 of the blender 14.

Inside of the blender 14, the various ingredients of the dry cementrecipe are blended together by dual shafts (not shown in FIGS. 6A and6B) being turned inside of the blender 14 by motors 74. After the drycement recipe is completely blended, together with all various additiveand constituent materials, it is discharged by gravity from the blender14 into ready mix hopper 84. When the product in the post-blend hopper74 is completely blended (oilfield terminology to describe the mixturebefore water is added to form slurry is “pre-blend”), the pre-blend ascontained in the pre-blend hopper 84 may be delivered to transportvehicle via transport conduit 86 or to pre-blend storage via storageconduit 88. If the pre-blend is to be stored, the storage conduit 88connects to fill valves 90 of pre-blend storage tanks 92. From thepre-blend storage tanks 92 the pre-blend contained therein may be loadedonto transport vehicles at the desired time via control valves 94 anddischarge ducts 96.

For almost all recipes of oil field cement blends for a particularformula, when switching to a different formula or recipe, there will beremnants of the prior mixture. To handle these remnants is a reclaimedstorage tank 98. For example, if the blender 14 has remnants of a drycement pre-blend therein when switching to a different blend, thoseremnants are pumped via reclaim line 100 to reclaim storage tank 98. Ifa transport vehicle has remnants remaining therein, they can also bepumped via reclaim valve 102 to the reclaim storage tank 98.

Likewise, if there are remnants left in pre-blend storage tanks 92 bypressurizing the pre-blend storage tanks 92 with compressor 104, anyremnants remaining therein can be pumped via reclaim line 100 by openingpre-blend reclaim valves 106 via reclaim line 100 into reclaim storagetank 98. Reclaim dust collector 108 prevents any dust during the reclaimprocess from being discharged to atmosphere.

To get rid of reclaim materials contained in the reclaim storage tank98, the compressor 104 pressurizes the reclaim storage tank 98 whichthen forces the reclaimed material out discharge control 110 fordelivery through transport ducts 112 for disposal. If it becomesnecessary for the reclaim storage tank 98 to vent to atmosphere, reclaimdust collectors 114 will ensure no dust is discharged to atmosphere.

Referring now to FIG. 7, the specially designed bearing 72 for theshafts 70 of the blender 14 is explained in further detail. Thespecially designed bearing consists of an annulus 116 being bolted tothe blender housing 118 by bolts 120 pressing plate 122 against theannulus 116.

Through the annulus 116 is a pressurized air fitting that connects viaair duct 126 to the shafts 70 to feed pressurized air from thecompressor 104 (see FIG. 6B) via the air duct 126 to the surface betweenbearing 128 and shaft 70. This means there is a cushion of air betweenbearing 128 and shaft 70. Also the pressurized air keeps the materialbeing mixed from getting into the area between bearing 128 and shaft 70.The shaft 70 is literally riding on a cushion of air.

Referring to FIG. 8, a pictorial flow representation of the atmosphericstorage mechanical weigh batch plant 12 as explained in FIGS. 1 and 2 isshown. Where possible, like numbers as used for FIGS. 1 and 2 will beused in FIG. 8. However, FIG. 8 will have additional reference numbersand explanations where necessary. The bulk storage tanks 20A-20F feedthrough conveyors 22A-22F, respectfully, into bulk weigh batcher 16.Delivery of bulk material from bulk storage tanks 20A, 20C, 20D and 20Eis controlled by butterfly valves 130. Because bulk storage tanks 20Band 20E are split tanks pneumatic actuated butterfly valves 132 areused. The bulk weigh batcher 16 has load cells 134 to accurately measurethe amount of bulk material that has been received. Once the properamount of material has been received into the bulk weigh batcher 16, itis then delivered via dual augers 18 to the blender 14. The bulk weighbatcher 16 handles the large quantities of materials that wouldtypically be used in a dry oilfield cement mixture. The quantities beinghandled by the bulk weigh batcher 16 are larger quantities(percentagewise) of the dry oilfield cement mixture.

At the intermediate storage tanks 36, bulk bags un-loaders 40A and 40Breceive the bags of material which bags of material are dumped into anintermediate storage tank 36 via drag tubes 42A and 42B.

Below the intermediate storage tank 36 are pneumatic actuated butterflyvalves 136 which controls the amount of intermediate material beingdelivered to the weigh vessel 48 as determined by load cells 138. Whenthe proper amount of intermediate material has been received into theweigh vessel 48, pneumatically actuated butterfly valve 140 is openedand the intermediate material is delivered through mechanical screwauger 50 to the blender 14. The term “intermediate” refers to amounts byweight that is considerably less than the materials delivered by thebulk weigh batcher 16, but are much greater than the small additivestypically mixed into a dry oilfield cement blend.

The mini batch facility 52 as is illustrated in FIG. 8, has a series ofweigh vessels 54A-54C that can accurately measure small amounts ofadditives and deliver those small amounts of additives via pneumaticallyactuated butterfly valves 142 through the drag tube 56. The drag tube 56will deliver the small amounts of additives to the blender 14.

Also the mini batch additive weighing portion of the overall facility 52will have a hand weigh batcher 58 for the hand adding of small amountsof various additives. The hand amounts also feed through one of thepneumatically actuated butterfly valves 142 into drag tube 56. Each ofthe weigh vessels 54A-54C has an opening 80 through which the smallamounts of additives can be stored. Even the hand weight batcher 58 hasa vessel 144 in which to store small amounts of additives. The minibatch facility 52 adds the small portions by weight of materials thatare necessary for the dry oilfield cement blend.

After the blender 14 has thoroughly forced the dry materials, into ablend, the dry oilfield cement blend is discharged into a post blendhopper holding pre-blended material 84 for either storage or delivery tothe well site. Blowers 146 may be used to move the dry pre-blendoilfield cement in hopper 84 typically referred to as “pre-blend”, toeither the transport vehicle (not shown) or a storage vessel 148. Thestorage vessel 148 could be the same as the pre-blend storage tanks 92as illustrated in FIG. 6B. The compressor 104 provides compressed air asneeded particularly in operating various pneumatic valves.

Turning to FIGS. 8 a and 8 b, the illustrative flow diagram of theatmospheric storage mechanical weigh batch blend plant of FIG. 8 isgiven along with the legends for each of the items illustrated beinglisted in FIG. 8 c. In this manner, each of the items shown in FIGS. 8 aand 8 b are controlled as illustrated in FIG. 8 a by each of the itemsas shown in the legend of FIG. 8 c. For example, any of the mechanicalfunctions are illustrated by symbols as are contained in the legend ofFIG. 8 c, such as “load cells”, “pneumatic actuator”, “slide gate”, justto name a few. The illustrative flow diagram as shown in FIGS. 8 a and 8b is the type an engineer would use. FIG. 8 c is the legend that goeswith FIGS. 8 a and 8 b.

Referring to FIGS. 8 d through 8 i in combination, the electricalconnections to FIGS. 8 a and 8 b are illustrated. Each of the tanks asillustrated in FIGS. 8 a and 8 b have the same numerical reference inFIGS. 8 d and 8 i. A motor control panel 200 is used to operate all ofthe controls as illustrated in FIGS. 8 a and 8 b. A description of theitem being operated is given in each of the blocks connected to themotor control panel 200. While a part of the motor control panel 200,the utility load center 202 controls specific parts of the weigh batchblend plant.

Also connected to the motor control panel 200 is additive scale panel204, which is used to add the small amounts added to the blend. Use ofthe term “J-box” as contained in FIGS. 8 d and 8 i is referring to anelectrical junction box.

The entire operation is run by a programmable logic controller 206 shownin FIG. 8 f, which programmable logic controller 206 sets the recipebeing used into the weight batch blending plant. Through the use of theprogrammable logic controller 206, the recipe can be changed accordingto the desires of the operator. In one particular oil field, the recipefor the cement may be different than in a different oil field.Therefore, the recipe may have to be changed, depending upon where theend product is being used.

Power for the programmable logic controller 206 is provided by computerpower unit 208. It is important that the computer power unit 208 not besubject to power fluctuations and has a backup power source to maintaininformation in memory.

In case any portion of the program needs to be overwritten, an overridepanel 210 allows the operator to overrun any portion of the plant as isnecessary. Through the use of the override panel 210, if necessary, theentire plant could be run manually.

FIGS. 8 a-8 i illustrate how a typical atmospheric storage mechanicalweigh batch blend plant may be controlled.

Blower 150 may be used to move any of the dry materials when blendingthe various ingredients.

While the blender 14 as shown in FIGS. 1, 2 and 3, is a dual shafthorizontal blender, the blender also could be a vertical shaft blender152 as illustrated in FIG. 9. The vertical shaft blender 152 has avertical vessel 154 with vertical shafts 156 extending there through.The vertical shafts 156 has paddles (not shown) thereon to blend thematerial contained within the vertical vessel 154. The dry materials forthe ready mix cement is delivered to the vertical vessel 154 via dualscrew auger 18 of the large quantities of materials, mechanical screwauger 50 for the intermediate materials, and drag tubes 56 for the smallamounts of additives. All of the materials are fed into the verticalhopper 158 or discharged through lower opening 160 into the verticalvessel 154. After the appropriate amounts of the various ingredients aredischarged through the vertical hopper 158 into the vertical vessel 154and thoroughly blended therein, the “pre-blend” cement mix is dischargedthrough discharge opening 162 into one of the pre-blend storage tanks92.

Typically, a vertical shaft blender 152 will be used for smallerbatches, but a horizontal shaft blender such as blender 14 is used forlarger batches.

What I claim is:
 1. An atmospheric storage batch-type blend plant forproviding a dry, pre-blended, cement prepared according to a recipe foruse in oil well encasement, said batch blend plant comprising: a blenderfor receiving measured, dry materials to be thoroughly blended into a anaccurate pre-blend, the blender having a blender housing, a shaftprotruding from the housing, and a bearing assembly attached to theblender housing and surrounding part of the shaft; a plurality of bulkstorage tanks; a bulk weigh batcher for measuring by weight bulkmaterials from said plurality of bulk storage tanks; bulk deliverydevice for delivering said bulk materials from said bulk weigh batcherto said blender; an intermediate weigh vessel for measuring by weightintermediate materials from intermediate storage tanks; an intermediatedelivery device for delivering said intermediate materials from saidintermediate weigh vessel to said blender; mini batch weigh vessels formeasuring by weight small amounts of additives; an additives deliverydevice for delivering small additives after said measuring to saidblender; said bulk weigh batcher measuring large quantities by weight,said mini batch weigh vessels measuring small quantities by weight andsaid intermediate weigh vessel measuring intermediate quantities byweight, all of which are mixed together to give said pre-blend;pre-blend containers for receiving said pre-blend after the weighing andblending of said recipe of said bulk materials, said intermediatematerials and said small amounts of said additives in said blender; anda source of pressurized air being connected to said bearing assembly toprovide said pressurized air between bearings in said bearing assemblyand said shaft to prevent abrasive materials from getting between saidbearings and said shaft.
 2. The atmospheric storage batch-type blendplant for providing said dry, pre-blended, cement prepared according tosaid recipe for use in oil well encasement as recited in claim 1 whereinsaid bulk delivery device is a bulk screw auger and intermediatedelivery device is an intermediate screw auger.
 3. The atmosphericstorage batch-type blend plant for providing said dry, pre-blended,cement prepared according to said recipe for use in oil well encasementas recited in claim 2 wherein said additives delivery device is dragtubes.
 4. The atmospheric storage batch-type blend plant for providingsaid dry, pre-blended, cement prepared according to said recipe for usein oil well encasement as recited in claim 3 wherein said blender is adual shaft horizontal blender with paddles being attached to saidshafts.
 5. The atmospheric storage batch-type blend plant for providingsaid dry, pre-blended, cement prepared according to said recipe for usein oil well encasement as recited in claim 4 comprising a bag un-loaderfor unloading bags of said intermediate material into said intermediatestorage tanks.
 6. The atmospheric storage batch-type blend plant forproviding said dry, pre-blended, cement prepared according to saidrecipe for use in oil well encasement as recited in claim 5 wherein saidmini batch weigh vessels includes a hand additive weight station forhand measuring hand weighted additives to be delivered to said blendervia said drag tubes.
 7. The atmospheric storage batch-type blend plantfor providing said dry, pre-blended, cement prepared according to saidrecipe for use in oil well encasement as recited in claim 3 wherein saidblender is a vertical shaft blender.
 8. The atmospheric storagebatch-type blend plant for providing said dry, pre-blended, cementprepared according to said recipe for use in oil well encasement asrecited in claim 6 or 7 wherein containers for such pre-blend arepre-blend storage tanks.
 9. The atmospheric storage batch-type blendplant for providing said dry, pre-blended, cement prepared according tosaid recipe for use in oil well encasement as recited in claim 8comprising a reclaim storage tank for receiving leftover materials fromsaid pre-blend for subsequent disposal.
 10. The blend plant of claim 1wherein said bearing assembly comprises: a cylindrical bearing surfacein said bearing surrounding part of the shaft; an annulus circumscribingthe bearing; and a fitting connected to the annulus and having a fittingend connected to said source of pressurized air, wherein the fitting,the annulus and the bearing at least partially define an air ductbetween the fitting end and the cylindrical bearing surface.